Two-stroke internal combustion engine with crankcase scavenging

ABSTRACT

The invention relates to a two-stroke internal combustion engine with crankcase scavenging, with an exhaust passage controlled by the piston and at least two first transfer passages and at least one second transfer passage, each with a corresponding transfer window into the cylinder chamber and a window on the crankcase side for communication between the cylinder chamber and the crankcase, the transfer windows of the first transfer passages being controlled by the upper edge of the piston, and the crankcase-side window of the second transfer passage being disposed in a region of the cylinder wall that is swept by the piston skirt of the piston. The cylinder wall comprises at least one recess, which is arranged in close vicinity to the transfer window of the second transfer passage and which is in flow communication with the second transfer passage, wherein a narrow passage is arranged between the recess and the second transfer passage.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a two-stroke internal combustion enginewith crankcase scavenging, with an exhaust passage controlled by thepiston and at least two first transfer passages and at least one secondtransfer passage, each with a transfer window into the cylinder chamberand a window on the crankcase side for communication between thecylinder chamber and the crankcase, the transfer windows of the firsttransfer passages being controlled by the upper edge of the piston, andthe crankcase-side window of the second transfer passage being disposedin a region of the cylinder wall that is swept by the piston skirt ofthe piston, wherein for control of the second transfer passage thepiston skirt of the piston be provided with a control opening in thearea of the crankcase-side window of the second transfer passage.

DESCRIPTION OF THE PRIOR ART

[0002] The U.S. Pat. No. 3,881,454 describes a two-stroke engineconstruction with a pair of main scavenging passages and an auxiliaryscavenging passage, in which a fuel injector is located. The piston isreciprocatable to open and close the exhaust, main and auxiliaryscavenging passages, which communicate at one end with the crankcase atleast as long as the auxiliary scavenging window is uncovered by thepiston. As the fuel injector is arranged near the entry of the auxiliaryscavenging passage into the combustion chamber the temperature of thenozzle becomes very high resulting in carbon deposits and higher wear.

[0003] In AT 399 913 B a two-stroke engine is described, where at leasttwo of the transfer or scavenging passages open earlier than the othersto obtain the desired scavenging results, i.e., at a time when thepressure in the cylinder still exceeds that in the crankcase, so thatexhaust gas will flow into these passages and push back the fresh chargeinside without entering the crankcase itself. The timing of thesetransfer passages is effected by the upper edge of the piston acting asa control edge. Fuel supply is effected via a carburetor into a feedpassage connected with the crankcase.

[0004] In AT 397 695 B an internal combustion engine is described, wherea fuel injector is positioned in the transfer passage, the injected fuelstream being directed towards the side of the piston top facing thecylinder chamber. The axis of the injected fuel stream forms an anglewith the piston axis that is smaller than 90°, so that the fuel willmostly hit the half of the flat and rotation-symmetrical piston topopposite of the exhaust window. The drawback of this configuration isthat strong scavenging losses are incurred in the lower speed range.Moreover, the time available for an injection cycle is limited by theopening period of the scavenging windows. For selection of the injectorthis may lead to problems with the dynamic range, i.e., the ratio ofidle quantity to full-load quantity. Because of the shortness of theinjection period the fuel is injected onto the piston edge and pistonrings, which will have negative effects on HC emissions and causewetting of the cylinder wall and wash off the lubrication film.

[0005] DE 196 27 040 A1 presents a two-stroke spark-ignition engine withfuel injection, where an injector is positioned in the cylinder wallnext to the cylinder chamber. This arrangement and the lack of aircirculation around the injector will lead to high temperatures and anincrease in carbon deposits at the injector nozzle. Other undesirableresults, which are caused by the direction of the injected fuel stream,will be the wetting of the cylinder wall and washing-off of thelubricating film.

[0006] Another two-stroke internal combustion engine is described inU.S. Pat. No. 5,443,045, where an injector passes through the cylinderwall into the cylinder. The injector faces the exhaust window at adownward angle, which will result in strong scavenging losses in thelower speed range. As the injector is positioned in that area of thecylinder wall that is swept during the compression stroke hightemperatures and increased build-up of carbon deposits at the injectornozzle will occur due to the lack of air circulation.

SUMMARY OF THE INVENTION

[0007] It is an object of the invention to overcome these disadvantagesand to propose a two-stroke internal combustion engine of the abovetype, where fuel losses and hydrocarbon emissions may be minimized in asimple manner for both high and low speeds and loads. Another object ofthe invention is to increase the service life of the injector.

[0008] According to the invention this is achieved by providing thatsaid cylinder wall comprises at least one recess and that at least oneinjector opens into said recess being arranged in close vicinity to saidtransfer window of said second transfer passage, wherein a narrowpassage is arranged between said recess and said second transferpassage. Disposing the injector in the recess which communicates withthe second transfer passage will considerably reduce carbon deposits asthe air circulation prevailing in this region will afford cooling, andwill enhance carburetion. Due to the narrow passage air flowing from thesecond transfer passage to the recess will be accelerated and thereforeimprove the cooling of the orifice of the injector.

[0009] It is provided in a preferred variant that the narrow passage isshaped by at least one groove in the cylinder wall. According to analternative embodiment the recess may also be shaped by a duct branchingoff from the second transfer passage and leading to the recess. If therecess is disposed above the transfer window of the second transferpassage, i.e., on the side of a combustion chamber top, the groove maybe arranged in the direction of the cylinder axis.

[0010] According to another embodiment of the invention the narrowpassage is shaped by a separating edge of a cross rib, said separatingedge dividing the recess from said transfer window of said secondtransfer passage. The distance between the separating edge and thecylinder axis is larger than the distance between the cylinder wall andthe cylinder axis.

[0011] According to a further embodiment of the invention a reduction ofcarbon deposits can be achieved by means of a separating edge beinglocated in at least one transfer passage between an upper and a loweredge of the second transfer window. The separating edge divides thesecond transfer window into an upper and lower region, wherein theseparating edge is at a larger distance from the cylinder axis than theupper or lower edge. If the edge of the piston passes the separatingedge, the lower region of the second transfer window will be closed.Between the separating edge and the piston there is a small gap throughwhich the intake flow passes into the upper region, flowing around andcooling the nozzle. The separating edge is formed by a cross rib, beingarranged at right angle to the cylinder axis.

[0012] The axes of the injectors may be positioned within a wide angularrange of α=20-140° relative to the cylinder axis or a parallel thereof.Moreover, the directions of the axis of the fuel stream coming from theinjector, i.e., the jet axis, and the injector axis may differ. In thisway the injection characteristics of the injector may be adjusted to therespective requirements.

[0013] It is provided in a preferred variant of the invention that atleast two second transfer passages be disposed on the side of theexhaust passage and, preferably, that the injector opening into at leastone recess or one second transfer passage faces the half of the cylinderchamber opposite of the exhaust passage. In this manner scavenginglosses may be kept exceedingly small.

[0014] In another variant of the invention the proposal is put forwardthat at least one second transfer passage be disposed on the side of thecylinder opposite of the exhaust passage. The second transfer passagemay be positioned in a symmetry plane containing the axis of the exhaustpassage and the cylinder axis.

[0015] To keep scavenging losses as small as possible it could also beprovided that at least two second transfer passages be positionedoutside of a symmetry plane containing the exhaust passage axis and thecylinder axis. In this context the jet axis of the injector—seen in thedirection towards the cylinder axis—should preferably be directed onto atransfer window of a transfer passage that is preferably diametricallyopposed.

[0016] In order to prevent the cylinder wall from being wetted by thefuel it may be provided that the jet axis of the injector—seen in thedirection towards the cylinder axis—be directed onto the exhaust windowof the exhaust passage.

[0017] To enable the first and second transfer passages to be timedindependently of each other, and to permit optimum fuel injection intothe cylinder chamber it may be provided that the upper edge of thetransfer window of the second transfer passage be at a smaller distancefrom the top of the combustion chamber than the upper edge of thetransfer window of the first transfer passage. This configuration isespecially suitable for use with rotation-symmetrical, flat piston tops.

[0018] In the instance of an internal combustion engine with severalinjectors per cylinder it may be provided by the invention that theinjection axes of the injectors disposed in second transfer passageshave different angles relative to each other and/or to the cylinder axisor a parallel of the cylinder axis. In this way injectors with differentinjection characteristics may be used, permitting carburetion to beadjusted to any operating state of the engine. One injector could beconfigured as full-load injector and another one as part-load injector,for example.

[0019] For optimum adjustment of the injection process to the respectiverequirements it may be provided in further development of the inventionthat the injector be configured as a multi-jet unit, with at least twofuel jets differing as regards fuel amounts and/or injection times,preferably.

[0020] Designing the internal combustion engine as proposed by theinvention will ensure that the transfer windows of the first and secondtransfer passages and the crankcase-side window of the at least onesecond transfer passage and the corresponding control opening aredisposed such that the first and second transfer passages will be timedin different stroke positions of the piston. Obviously, the transferpassages could also be arranged so that the first and second transferpassages are controlled roughly simultaneously though by means ofdifferent control edges.

DESCRIPTION OF THE DRAWINGS

[0021] Following is a more detailed description of the invention asillustrated by the accompanying drawing, in which

[0022]FIG. 1 is a schematic representation of a two-stroke internalcombustion engine according to a first embodiment of the invention, inlongitudinal section, and

[0023]FIG. 2 represents this engine in plan view, seen in the directionof the cylinder axis,

[0024]FIG. 3 is a detail view of the second transfer window according tosaid first embodiment,

[0025]FIG. 4 is a detail view of the second transfer window in a secondembodiment of the invention,

[0026]FIG. 5 is an oblique view of transfers passages in a thirdembodiment of the invention, seen in the direction of the secondtransfer passage,

[0027]FIG. 6 is an oblique view of transfer passages in said thirdembodiment, seen in the direction of the exhaust passage,

[0028]FIG. 7 is an oblique view of transfer passages in a fourthembodiment of the invention, seen in the direction of the secondtransfer passage,

[0029]FIG. 8 is an oblique view of transfer passages in said fourthembodiment, seen in the direction of the second transfer passage,

[0030]FIG. 9 is an oblique view of transfer passages in a fifthembodiment of the invention and

[0031]FIG. 10 is another oblique view of transfer passages in said fifthembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0032]FIG. 1 shows a two-stroke internal combustion engine according tothe invention in axial view, where several first transfer passages 2along the periphery of the cylinder wall 1 b and at least one secondtransfer passage 2 a open into the cylinder chamber 1, forming transferwindows 12, 12 a, which are complemented by an exhaust passage 3 with anexhaust window 13. The cylinder casing is referred to as 20, whilst 11denotes an ignition source in the combustion chamber top 1 a.

[0033] The upper edge 12 a′ of the second transfer window 12 a is at asmaller distance from the combustion chamber top 1 a than the upperedges 12′ of the first transfer windows 12. On the crankcase side thesecond transfer passage 2 a opens into the cylinder wall 1 b, thecrankcase-side window bearing reference numeral 22. Control of thesecond transfer passage 2 a is effected via a control opening 40 in thepiston skirt 41 of the piston 4.

[0034] According to a first embodiment of the invention shown in FIGS. 1to 3 in the second transfer passage 2 a an injector 5 is disposed, whosefuel stream or injection jet 7 passes through the transfer window 12 ainto the cylinder chamber 1. The jet axis 7′ of the injection jet 7 hasan angle α of 20° to 140° relative to the cylinder axis 10 or a parallelof the cylinder axis 10. Due to the position of the second transferpassage 2 a there is considerable liberty in choosing the direction ofthe injector 5 within the range indicated in FIG. 1 by the angle P. Theextreme positions of the jet axis are denoted by 7 a′ and 7 b′.

[0035] By arranging the transfer window 12 a of the second transferpassage 2 a above the transfer windows 12 of the first transfer passages2, and as control of the second transfer passage 2 a is effected not bythe upper edge 4 a of the piston 4 but via a separate control opening 22whose control edges are referred to as 22 a, the timing of the first andsecond transfer passages 2, 2 a and fuel injection via the injector 5may be decoupled, and intake flow and injection characteristics may beadjusted to the respective requirements. As a consequence, HC emissionsand fuel consumption may be kept extremely low under both part-load andfull-load conditions. By disposing the injector 5 in the second transferpassage 2 a the injector nozzles 5 b are well protected against thebuild-up of carbon deposits. The direction of the injected fuel streamis chosen so as to prevent the fuel from wetting the cylinder wall.

[0036] Between an upper edge 12 a′ and a lower edge 12 a″ of the secondtransfer window 12 a separating edge 12 a′″ is arranged in the secondtransfer passage 2 a dividing the second transfer window 12 a into alower region 21 a and an upper region 21 b. The separating edge 12 a′″being formed by a cross rib 25 is arranged at right angle to thecylinder axis 10 as illustrated in FIGS. 1 and 3.

[0037] The separating edge 12 a′″ is at a larger distance from thecylinder axis 10 than the upper edge 12 a′ and the lower edge 12 a″ andforms a narrow passage 28 between upper region 21 b and lower region 21a of the second transfer passage 2 a. If the upper edge 4 a of thepiston 4 gets to a position near to the separating edge 12 a′″ the lowerregion 21 a of the second transfer window 12 a is almost closed except asmall gap 27 between the separating edge 12′″ and the piston 4 when thepiston 4 is taking a position which is indicated in FIG. 1 with brokenlines. The gap 27 forms the narrow passage 28 and causes an accelerationof the passing intake flow. Intake flow of the second transfer passage 2a passing the gap 27 gushes to the upper region 21 b and cools thenozzle 5 b of the injector 5. Therefore overheating of the nozzle 5 b ofthe injector 5 can be avoided. The cross section of the upper region 21b may be smaller than the cross section of the lower region 21 a.

[0038] Alternatively or further to the cross rib 25 the injector 5 maybe disposed in a recess 26 of the upper region 21 b of the secondtransfer passage 2 a. FIG. 4 shows such a second embodiment of theinvention with an injector 5 opening into a recess 26.

[0039]FIG. 2 gives a plan view of the internal combustion engine withpossible configurations for the second transfer passage 2 a and theinjector 5. A denotes a first configuration, in which the secondtransfer passage 2 a is located next to the exhaust passage 3, and thejet axis 7′ of the fuel jet 7 injected by the injector 5 runs in thedirection of the transfer window 12 a of a first transfer passage 2 thatis diametrically opposed to the injector 5. The direction of the jetaxis 7′ may differ from that of the injector axis 5′ and be inclinedthereto at an angle of up to 30°, approximately. B indicates a secondconfiguration for a second transfer passage 2 a, in which the jet axis7′ of the injector 5 not shown here in detail runs towards the transferwindow 12 a of a second transfer passage 2 a disposed laterally. Thetransfer window 12 a is essentially positioned opposite the exhaustwindow 13. Configuration C differs from configuration B in that the jetaxis 7′ of the injector 5 points towards the exhaust window 13.

[0040] The common feature of variants A, B and C is that the secondtransfer passage 2 a does not lie in a symmetry plane 10 a going throughthe cylinder axis 10 and axis 3 a of the exhaust passage 3.

[0041] In a fourth configuration denoted D the second transfer passage 2a including the injector 5 is disposed in the symmetry plane 10 a. Bysuitable choice of the inclination angle α between the jet axis 7′ ofthe injector 5 and the cylinder axis 10 or a parallel thereto scavenginglosses may be avoided. It should be understood that a combination ofvariants A, B, C, D is possible, where several injectors 5 withdifferent injection characteristics may be provided.

[0042] It is further possible to configure the injector 5 as a multi-jetunit, for example, a two-jet injector, where the injected fuel amountsas well as beginning and/or end of injection of the individual fuelstreams may differ.

[0043]FIGS. 5 and 6 show first transfer passages 102, second transferpassages 102 a, exhaust passages 103 and auxiliary exhaust passages 103a of a two-stroke internal combustion engine according to a thirdembodiment of the invention. Similar to said third embodiment FIGS. 7and 8 give oblique views of a fourth embodiment of the invention. Forreasons of clearity cylinder, piston, ignition source and cylindercasing are not shown in FIGS. 5 to 8.

[0044] Similar to the first and second embodiment shown in FIGS. 1 to 4the first and second transfer passages 102, 102 a open into the cylinderchamber (not shown in FIGS. 5 and 6), forming transfer windows 112, 112a, which are complemented by the exhaust passage 103 and auxiliaryexhaust passages 103 a with exhaust windows 113, 113 a.

[0045] Unlike the first and second embodiment in the third and fourthembodiment at least one injector 105 opens into a recess 126 which isformed in the cylinder wall. The recess 126 is in flow communicationwith the second transfer passage 102 a via a narrow passage 128, whichis shaped by at least one groove 127 formed in the cylinder wall. If thepiston gets to a position near the groove 127, the second transferpassage 102 a and the recess 126 are separated with the exception of thegroove 127. Intake flow of the second transfer passage 102 a passing thegroove 127 gushes to the recess 126 with high speed and cools the nozzle105 b of the injector 105.

[0046] In the third embodiment shown in FIGS. 5 and 6 there is onerecess 126, one groove 127 per injector 105. In contrast to this in thefourth embodiment shown in FIGS. 7 and 8 both injectors 105 open intothe same recess 126. Piston, exhaust passages and ignition source arenot shown in FIGS. 9 and 10.

[0047]FIGS. 9 and 10 show first transfer passages 202, second transferpassages 202 a and cylinder chamber 201 of a two-stroke combustionengine according to a fourth embodiment of the invention. The narrowpassage 228 is shaped by a duct 227, which branches off from the secondtransfer passage 202 a and leads to the recess 226. If the piston getsto a piston covering the transfer window 212 a of the second transferpassage 202 a, the second transfer passage 202 a and the recess 226 areseparated with the exception of the duct 227. Intake flow of the secondtransfer passage 202 a passing the duct 227 gushes to the recess 226with high speed and cools the nozzles 205 b of the injector 205.

I claim:
 1. A two-stroke internal combustion engine with crankcasescavenging, with an exhaust passage controlled by a piston and at leasttwo first transfer passages and at least one second transfer passage,each with a transfer window into a cylinder chamber and a crankcase-sidewindow for communication between the cylinder chamber and a crankcase,the transfer windows of the first transfer passages being controlled bythe upper edge of the piston, and the crankcase-side window of thesecond transfer passage being disposed in a region of a cylinder wallthat is swept by a piston skirt of the piston, wherein for control ofthe second transfer passage the piston skirt of the piston is providedwith a control opening in the area of the crankcase-side window of thesecond transfer passage, wherein said cylinder wall comprises at leastone recess, wherein at least one injector opens into said recess beingarranged in close vicinity to said transfer window of said secondtransfer passage, and wherein a narrow passage is arranged between saidrecess and said second transfer passage.
 2. The two-stroke internalcombustion engine according to claim 1, wherein the narrow passage isshaped by at least one groove in the cylinder wall between said recessand said transfer window of said second transfer passage.
 3. Thetwo-stroke internal combustion engine according to claim 1, wherein thenarrow passage is configured as a gap, which is shaped by a separatingedge dividing the recess from said transfer window of said secondtransfer passage.
 4. The two-stroke internal combustion engine accordingto claim 3, wherein the distance between separating edge and cylinderaxis is larger than the distance between cylinder wall and cylinderaxis.
 5. The two-stroke internal combustion engine according to claim 3,wherein the separating edge is arranged at right angle to the cylinderaxis.
 6. The two-stroke internal combustion engine according to claim 1,wherein the recess is disposed above the transfer window of the secondtransfer passage on the side of a combustion chamber top.
 7. Thetwo-stroke internal combustion engine according to claim 1, wherein atleast two injectors open into one recess.
 8. The two-stroke internalcombustion engine according to claim 1, wherein the narrow passage isshaped by at least one duct being formed in a cylinder casing.
 9. Thetwo-stroke internal combustion engine according to claim 1, wherein ajet axis of the fuel injector forms an angle of 20° to 140° with acylinder axis.
 10. The two-stroke internal combustion engine accordingto claim 1, wherein the directions of the jet axis and the injector axisdiffer.
 11. The two-stroke internal combustion engine according to claim1, wherein at least two second transfer passages are disposed on theside of the exhaust passage.
 12. An two-stroke internal combustionengine according to claim 1, wherein the injector opening into at leastone recess faces a half of the cylinder chamber opposite of the exhaustpassage.
 13. The two-stroke internal combustion engine according toclaim 1, wherein at least one second transfer passage is disposed on theside of the cylinder opposite of the exhaust passage.
 14. The two-strokeinternal combustion engine according to claim 1, wherein the secondtransfer passage is positioned in a symmetry plane containing an exhaustpassage axis and the cylinder axis.
 15. The two-stroke internalcombustion engine according to claim 1, wherein at least two secondtransfer passages are positioned outside of the symmetry planecontaining the exhaust passage axis and the cylinder axis.
 16. Thetwo-stroke internal combustion engine according to claim 1, wherein thejet axis of the injector—seen in the direction towards the cylinderaxis'is directed onto an exhaust window of the exhaust passage.
 17. Thetwo-stroke internal combustion engine according to claim 1, wherein thejet axis of the injector—seen in the direction towards the cylinderaxis—is directed onto a diametrically opposed transfer window of atransfer passage.
 18. The two-stroke internal combustion engineaccording to claim 1, wherein an upper edge of the transfer window ofthe second transfer passage is at a smaller distance from a combustionchamber top than the upper edge of the transfer window of the firsttransfer passage.
 19. The two-stroke internal combustion engineaccording to claim 1 with several injectors per cylinder, wherein theinjection axes of the injectors disposed in second transfer passageshave different angles relative to each other.
 20. The two-strokeinternal combustion engine according to claim 1 with several injectorsper cylinder, wherein the injectors have different injectioncharacteristics, at least one injector being configured as a full-loadinjector and at least one other injector as part-load injector.
 21. Thetwo-stroke internal combustion engine according to claim 1, wherein thetransfer windows of the first and second transfer passages and acrankcase-side window of the at least one second transfer passage andthe corresponding control opening are disposed such that the first andsecond transfer passages will be timed in different stroke positions ofthe piston.
 22. The two-stroke internal combustion engine according toclaim 1, wherein the injector is configured as a multi-jet unit.
 23. Thetwo-stroke internal combustion engine according to claim 1, wherein theinjector is configured as a multi-jet unit with at least two fuel jetsdiffering as regards fuel amounts and injection times.
 24. A two-strokeinternal combustion engine with crankcase scavenging, with an exhaustpassage controlled by a piston and at least two first transfer passagesand at least one second transfer passage, each with a transfer windowinto a cylinder chamber and a crankcase-side window for communicationbetween the cylinder chamber and a crankcase, the transfer windows ofthe first transfer passages being controlled by the upper edge of thepiston, and the crankcase-side window of the second transfer passagebeing disposed in a region of a cylinder wall that is swept by a pistonskirt of the piston, wherein for control of the second transfer passagethe piston skirt of the piston is provided with a control opening in thearea of the crankcase-side window of the second transfer passage,wherein a separating edge is located in at least one second transferpassage between an upper and a lower edge of said second transferwindow, said separating edge dividing the second transfer window into anupper and a lower region, the distance between separating edge andcylinder axis being larger than the distance between upper edge and thecylinder axis, and wherein at least one injector opens into the upperregion of at least one second transfer passage, wherein the separatingedge is shaped by a cross rib, and wherein the separating edge isarranged at right angle to the cylinder axis.
 25. The two-strokeinternal combustion engine according to claim 24, wherein a jet axis ofthe fuel injector forms an angle of 20° to 140° with a cylinder axis.26. The two-stroke internal combustion engine according to claim 24,wherein the directions of the jet axis and the injector axis differ. 27.The two-stroke internal combustion engine according to claim 24, whereinat least two second transfer passages are disposed on the side of theexhaust passage.
 28. An two-stroke internal combustion engine accordingto claim 24, wherein the injector opening into at least one secondtransfer passage faces a half of the cylinder chamber opposite of theexhaust passage.
 29. The two-stroke internal combustion engine accordingto claim 24, wherein at least one second transfer passage is disposed onthe side of the cylinder opposite of the exhaust passage.
 30. Thetwo-stroke internal combustion engine according to claim 24, wherein thesecond transfer passage is positioned in a symmetry plane containing anexhaust passage axis and the cylinder axis.
 31. The two-stroke internalcombustion engine according to claim 24, wherein at least two secondtransfer passages are positioned outside of the symmetry planecontaining the exhaust passage axis and the cylinder axis.
 32. Thetwo-stroke internal combustion engine according to claim 24, wherein thejet axis of the injector—seen in the direction towards the cylinderaxis—is directed onto an exhaust window of the exhaust passage.
 33. Thetwo-stroke internal combustion engine according to claim 24, wherein thejet axis of the injector—seen in the direction towards the cylinderaxis—is directed onto a diametrically opposed transfer window of atransfer passage.
 34. The two-stroke internal combustion engineaccording to claim 24, wherein an upper edge of the transfer window ofthe second transfer passage is at a smaller distance from a combustionchamber top than the upper edge of the transfer window of the firsttransfer passage.
 35. The two-stroke internal combustion engineaccording to claim 24 with several injectors per cylinder, wherein theinjection axes of the injectors disposed in second transfer passageshave different angles relative to each other.
 36. The two-strokeinternal combustion engine according to claim 24 with several injectorsper cylinder, wherein the injectors have different injectioncharacteristics, at least one injector being configured as a full-loadinjector and at least one other injector as part-load injector.
 37. Thetwo-stroke internal combustion engine according to claim 24, wherein thetransfer windows of the first and second transfer passages and acrankcase-side window of the at least one second transfer passage andthe corresponding control opening are disposed such that the first andsecond transfer passages will be timed in different stroke positions ofthe piston.
 38. The two-stroke internal combustion engine according toclaim 24, wherein the injector is configured as a multi-jet unit. 39.The two-stroke internal combustion engine according to claim 24, whereinthe injector is configured as a multi-jet unit with at least two fueljets differing as regards fuel amounts and injection times.